Many instances exist of message-based exchanges of information between systems and/or devices. For example, operations of certain software applications may require, or may benefit from, access to data, functionality, or other information that is external to the software applications. The software applications may gain access to some such information through the use of message exchanges with hardware and/or software components, referred to generally as nodes, that are designed to provide such information. More specifically, for example, it may occur that the software applications are highly specialized to perform their particular functionalities, and may not be designed or optimized to execute message exchanges with the nodes providing the desired information. Consequently, messaging or other middleware components may be used to facilitate message exchanges between the software applications and the nodes.
In practice, it may occur that some of these nodes are only intermittently-available to the middleware component(s). For example, some such nodes may be mobile, such as when a node includes, or is associated with, a vehicle (such as, for example, a truck or a car). Other mobile nodes may include mobile computing devices (such as, for example, mobile phones or personal digital assistants), or persons who are equipped with various types of computing equipment. Other nodes may be stationary, but may be intermittently available by virtue of periodically reducing or deactivating a power source used for data transmission.
Thus, such intermittently-available nodes may experience connected phases (e.g., when they are in range or otherwise in communication with a middleware component), and non-connected phases (e.g., when communication with the middleware component is unavailable). In practice, such intermittent availability may result in an inability of the middleware component to exchange one or more messages with the node(s) at any particular time, such as during a non-connected phase. Consequently, an operator of the software application(s) and the middleware component may not be aware, with sufficient specificity, of whether and when a particular message exchange can or will occur.
In such situations, a time-to-live (TTL) may be associated with a message to be sent to the node, so that if the message resides in the middleware component for an amount of time equal to or greater than the time-to-live, then the message may expire and an error may be provided to the operator. Such a solution provides certain advantages, such as, for example, avoiding circumstances where messages grow stale or outdated within the middleware component. However, such a solution, by itself, does not actually provide the operator with sufficient information as to whether and when a successful message exchange may occur, but, rather, merely provides information as to a time after which the message exchange may not occur (at least, without further action). Moreover, to obtain even this information regarding the non-occurrence of the desired message exchange, the operator may be required to wait an entirety of the time-to-live of the message in question.
In so doing, an efficiency of the software application(s) and middleware component may be reduced. For example, the middleware component may become clogged with messages which have no realistic chance of being delivered before their times-to-live expire, yet the middleware component may nonetheless wait the entirety of the time-to-live for each such message before discarding the message(s). As another example, without knowledge of when the intermittently-available node will be available for delivery of a particular message, it may be difficult for the operator to optimize scheduling of desired message exchanges.